Field of the Invention
This invention relates generally to techniques for joining sandwich structures having an inner core and, more particularly, to techniques for butt welding sandwich structures, such as vehicle structures, that includes providing a cooling fluid barrier at an end of the core that prevents cooling fluid from entering the core during the welding process.
Discussion of the Related Art
Vehicles include various support structures, such as vehicle floor beams and side beams, that provide support and to which other structures are mounted. For example, vehicle floor beams are sometimes welded to vehicle side rails. Various parts of the vehicle require different degrees of strength, where it is typically desirable to make those structures as light weight as possible. Some of those structures may be sandwich structures, where the particular structure includes an outer layer, such as an aluminum layer, and an inner core, sometimes made of a light weight material, such as a foam, and other times a structural core, such as micro-truss structures. Using such sandwich structures as structural elements is beneficial in that it typically reduces the mass of the vehicle without compromising strength. In some cases, it becomes necessary to join two sandwich structures together by a high integrity bond. If the process for joining such sandwich structures together cannot provide a high integrity joint, then the ability to provide such light weight high strength structures becomes irrelevant. This problem becomes even greater if the sandwich structures are different.
It is known in the art to fabricate a three-dimensional micro-truss polymer structure for various structural uses. For example, U.S. Pat. Nos. 7,653,279 and 7,382,959 disclose a process for fabricating such a micro-truss structure. Generally, the process includes providing a reservoir or mold filled with a volume of a curable monomer and covered by a mask including strategically positioned apertures. Light sources are positioned relative to the mask and light from the light sources shinning through the apertures cures and hardens interconnected polymer columns, referred to herein as struts, to form a rigid support structure. Once the columns are cured, the struts are formed and the light sources are turned off, the reservoir is emptied of the non-cured monomer that did not receive the light so that the resulting hard polymer structure forms the micro-truss structure having an array of spaced apart struts.